Document NE1p16bv8D84R4OM5p04a0ZGw

Heating Ventilating Air Conditioning Guide 1939 content per pound of the vapor is 207.8 Btu. Also that the heat content of the liquid is 42.2 Btu per pound. Subtract 42.2 from 207.8 and 165.6 Btu per pound is the heat necessary to change the liquid refrigerant to a vapor (latent heat). As the heat to accomplish this change comes from the air around the coil, the heat removed from the air is 165.6 Btu per pound of methyl chloride evaporated in the coil. When the refriger ant is circulated at 2 lb per minute, 2 X 165.6, or 331.2 Btu per minute are removed from the air, or refrigerating effect is produced at the rate of 331.2 -s- 200, or 1.65 tons. 4 0 Calculate the dew-point, wet-bulb, relative humidity and absolute hu midity of air in equilibrium at 100 F with pure lithium chloride solution of .density 1.270. From Table 8 the concentration of a solution of density 1.270 at 100 F is 18.0 M. From Table 7 the dew-point of 18 M lithium chloride at 100 F is 43.7 F. From Table. 6, Chapter 1, the partial pressure of water over the solution is 0.2858 in. of Hg, the absolute humidity is 42.00 grains per pound dry air, and the wet-bulb is 65.8 F. The relative humidity is 14.0 per cent. 5 0 Calculate the boiling point, and freezing point of 18 M lithium chloride solutions. From Table 10, boiling point (standard) is 285.8 F, freezing point is 58.1 F. The salt precipitated on cooling to this temperature has the composition LiCl-2HsO. 6 0 Calculate the heat of vaporization of 1 lb of water from a large amount of lithium chloride solution at the boiling point. The heat of boiling is equal to the heat of mixing plus the heat of boiling pure water at the same temperature. The heat of mixing from Table 10 at 18 M and 285.8 F is (145 -- 0.186 X 285.8) = 92 Btu per pound. The heat of vaporization of water from steam tables at 285.8 F is 920 Btu per pound. Therefore the heat of vaporization of water from the solution is 920 + 92 = 1012 Btu per pound. 7 0 One thousand pounds of air per minute at 100 F dry-bulb with a dew-point of70 F and a relative humidity of 39 per cent is passed over 184/ lithium chloride solution. The rate of flow of the solution is 200 gpm and the entering tempera ture is 80 F. The air leaves the absorber at 85 F dry-bulb and dew-point of 35 F. Calculate (a) the heat to be removed from the lithium chloride solution to maintain these conditions, and (6) the temperature rise of the solution in passing through the absorber. o. The heat content of the entering air: From Table 6, Chapter 1, weight of vapdr at 70 F dew-point is 0.01574 lb times heat content of steam at 100 F dry-bulb is 1104.2 (Table 8, Chapter 1) equals 17.41 Btu per pound plus heat content of dry air at 10(^F is 24.0 (Table 6, Chapter 1) resulting in heat content of mixture as 41.41 Btu per pound. Similarly, the heat content of the leaving air: Weight of vapor at 35 F dew-point is 0.004262 X 1097.5 == 4.68 Btu per pound plus heat content of dry air at 85 F is 20.39 resulting in heat content of mixture as 25.07 Btu per pound. j Heat to be extracted from air is 1000 X (41.41 -- 25.07) *= 16,340 Btu per minute. Add to this the heat of mixing of 18M lithium chloride at 80 F equals 145 -- (0.186 X 80) = 130 Btu per pound (Table 10) or for 1000 lb of air X (0.01574 - 0.00426) X 130 = 1494 Btu per minute. Heat to be removed from solution is 16,340 + 1494 = 17,834 Btu per minute. 6. The weight of solution circulated is 200 X 1.275 (Table 8) X 8.33 *= 2124 lb per minute. Its heat capacity is 2124 X 0.631 (Table 10) = 1340 Btu per minute per degree Fahrenheit. The temperature rise is 17,834 -5- 1340 = 13.31 F. Chapter 3 PHYSICAL AND PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING Vitiation o Air, Heat Regulation in Man, Effects of Heat, Effects of Cold and Temperature Changes, Acclimatization, Effective Temperature Index of Warmth, Optimum Air Condi tions, Winter and Summer Comfort Zone, Optimum Humid ity, Air Quality and Quantity, Air Movement and Distribution, Natural and Mechanical Ventilation, Heat and Moisture Losses, Ultra-Violet Radiation and Ionization, Recirculation and Ozone, Ventilation Standards VENTILATION is defined in part as "the process of supplying or removing air by natural or mechanical means to or from any space." (See Chapter 45). The word in itself implies quantity but not necessarily quality. From the standpoint of comfort and health, however, the problem is now considered to be one of securing air of the proper quality rather than of supplying a given quantity. The term air conditioning in its broadest sense implies control of any or all of the physical or chemical qualities of the air. More particularly, it includes the simultaneous control of temperature, humidity, movement, and purity of the air. The term is broad enough to embrace whatever other additional factors may be found desirable for maintaining the atmosphere of occupied spaces at a condition best suited to the physio logical requirements of the human body. VITIATION OF AIR Under the artificial conditions of indoor life, the air undergoes certain physical and chemical changes which are brought about by the occupants themselves. The oxygen content is somewhat reduced, and the carbon dioxide slightly increased by the respiratory processes. Organic matter, which is usually perceived as odors, comes from the nose, mouth, skin and clothing. The temperature of the air is increased by the metabolic processes, and the humidity raised by the moisture emitted from the skin and lungs. There is also a marked decrease in both positive and negative ions in the air of occupied rooms but the significance of this factor is still questionable1. Contrary to old theories, the usual changes in oxygen and carbon dioxide are of no physiological concern because they are much too small even under the worst conditions. The amount of carbon dioxide in air is `A.S.H.V.E. Research Report No. 921--Changes in Ionic Content in Occupied Rooms Ventilated by Natural and Mechanical Methods, by C. P. Yaglou, L. C- Benjamin and S. P. Choate (A.S.H.V.H. Transactions. Vol. 38. 1932. p. 191).